1. Field of the Invention
The invention relates generally to a motor driven fluid apparatus and, more particularly, to a motor driven fluid apparatus having compression and drive mechanisms within a hermetically sealed container.
2. Description of the Related Art
Motor driven fluid apparatuses having compression and drive mechanisms within a hermetically sealed housing for use in a refrigeration circuit are generally well-known. For example, in FIG. 3 of Japanese Patent Application Publication No. 1-178799 ("Japanese '799"), there is shown a compressor having a hermetically sealed housing which encloses a compression mechanism, such as a scroll-type compression mechanism, and a drive mechanism therein. The drive mechanism comprises a drive shaft and a motor for rotating the drive shaft. The motor comprises a rotor, which is operatively coupled to the drive shaft, and a stator assembly surrounding the rotor with a small radial air gap therebetween.
Typically, the motor of Japanese '799 is provided with a stator assembly as disclosed in U.S. Pat. No. 4,215,464 to Miller ("Miller"). The stator assembly comprises an annular magnetic core having a plurality of axially extending slots, which are formed at an inner peripheral surface of the core, and a plurality of windings, each having a plurality of coils formed by multiple turns of an enamel-coated conductor. The multiple turns of the conductor have side turn portions, which are disposed within the axially extending slots, and end turn portions, which project axially from the slots and are disposed about the axial end surfaces of the core. The windings are electrically connected to each other and to one end of the conductor leads in various configurations depending on a variety of factors, such as the number of windings and whether the windings are to be connected in parallel or in series.
If the above-described electrical interconnections are not properly insulated, electricity from the interconnections may be conducted, for example, by a refrigerant contained within the housing, to other parts of the apparatus, such as the housing. This unintentional conduction of electricity can result in an unsafe and offensive electrical shock when, for example, a person touches the housing to service the components therein. In order to prevent this unintentional conduction of electricity, the connection points of the electrical interconnections in Miller are covered by plastic tubular members having an electrical insulation characteristic. Further, the connection points are generally disposed within or about one of the end turn portions of the multiple turns of the conductor.
The other end of the conductor leads is electrically connected to one end of a plurality of external power conductor terminals, which are fixedly and insulatingly held by an insulating base. Typically, the base is fixedly and hermetically secured to the housing. Further, as shown in Japanese Patent Application Publication No. 4-81581 ("Japanese '581"), in order to prevent unintentional conduction of electricity from the above-described electrical interconnections, the connection points are hermetically coated with a plastic having electrical insulation and anti-heat characteristics.
Several problems result, however, from these prior insulation structures. For instance, the connection points between the windings themselves, and between the windings and the one end of the conductor leads, are only insulated by the tubular members. Therefore, air gaps or apertures between the connection points and the tubular members are typically created, thereby resulting in insufficient and/or inefficient electrical insulation.
Additionally, apertures, e.g., pin holes, can unexpectedly form at an exterior surface of the end turn portions of the multiple turns of the enamel-coated conductor. Other apertures can also form, for example, by portions of the enamel unexpectedly separating at the exterior surface of the end turn portions. This formation of apertures can occur, for example, while transporting the stator assembly or setting a configuration of the end portions of the multiple turns. Typically, these apertures also result in insufficient electrical insulation.
As described above, because of these and other shortcomings of prior insulation structures, a person may receive an unsafe and offensive electric shock when he or she touches the compressor housing in order to service the components therein. Electric shock is especially likely if a refrigerant having a relatively high conductivity, such as C.sub.2 H.sub.2 F.sub.4 (HFC-134a) or CClHF.sub.2 (HCFC-22), is charged into the refrigerant circuit while the compressor operates in a situation where a suction chamber of the compressor housing is in a liquid-rich state. In this situation, the relatively high conductivity of the refrigerant excessively increases the amount of electricity which is conducted by the refrigerant to the housing from the above-described connection points, pin holes, and separated portions of enamel coating.
Other problems typically result from conventional structures for insulating electrical interconnections in motor driven fluid apparatuses.